This is a note to let you know that I've just added the patch titled
Revert "userfaultfd: don't fail on unrecognized features"
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-userfaultfd-don-t-fail-on-unrecognized-features.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2ff559f31a5d50c31a3f9d849f8af90dc36c7105 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@xxxxxxxxxx>
Date: Wed, 12 Apr 2023 12:38:52 -0400
Subject: Revert "userfaultfd: don't fail on unrecognized features"
From: Peter Xu <peterx@xxxxxxxxxx>
commit 2ff559f31a5d50c31a3f9d849f8af90dc36c7105 upstream.
This is a proposal to revert commit 914eedcb9ba0ff53c33808.
I found this when writing a simple UFFDIO_API test to be the first unit
test in this set. Two things breaks with the commit:
- UFFDIO_API check was lost and missing. According to man page, the
kernel should reject ioctl(UFFDIO_API) if uffdio_api.api != 0xaa. This
check is needed if the api version will be extended in the future, or
user app won't be able to identify which is a new kernel.
- Feature flags checks were removed, which means UFFDIO_API with a
feature that does not exist will also succeed. According to the man
page, we should (and it makes sense) to reject ioctl(UFFDIO_API) if
unknown features passed in.
Link: https://lore.kernel.org/r/20220722201513.1624158-1-axelrasmussen@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230412163922.327282-2-peterx@xxxxxxxxxx
Fixes: 914eedcb9ba0 ("userfaultfd: don't fail on unrecognized features")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1966,8 +1966,10 @@ static int userfaultfd_api(struct userfa
ret = -EFAULT;
if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
goto out;
- /* Ignore unsupported features (userspace built against newer kernel) */
- features = uffdio_api.features & UFFD_API_FEATURES;
+ features = uffdio_api.features;
+ ret = -EINVAL;
+ if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
+ goto err_out;
ret = -EPERM;
if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
goto err_out;
Patches currently in stable-queue which might be from peterx@xxxxxxxxxx are
queue-6.2/revert-userfaultfd-don-t-fail-on-unrecognized-features.patch
